Follies is a dazzling musical by Stephen Sondheim (A Little Night Music, Sweeney Todd, Sunday in the Park with George), performed for the first time on the National Theatre’s Olivier stage. The cast includes Imelda Staunton, who was recently on NT Live screens in Who’s Afraid of Virginia Woolf?, Tracie Bennett and Janie Dee; and the production will also include a 21-piece orchestra. It promises to be a visual and musical extravaganza.